doctype
html
    head
        meta(charset='utf-8')
        title jade example
        style.
            div
            {width:100px;height:100px;background:#ccc;text-align:center;line-height:100px;float:left;margin:10px auto}
            div.last {clear:left}
        body
            -var a=0;
            while a<12
                if a%4==0&&a!=0
                    div.last=a++
                else
                    div=a++